Also, the piston braces of known pistons project radially outward relatively far from the piston axis so as to provide sufficient space for the movement of the tilting plate or tilting ring and the piston shoes, while being sufficiently stiff to prevent the piston shoes from falling out.
Moreover, in tilting-ring or tilting-plate type compressors, the lubrication of the radially outward sliding surface of the brace between the piston and the housing is of great importance, especially if, when using CO2 as the refrigerant, the machine dimensions are smaller than in conventional refrigerant compressors because of the high pressures. As a consequence of the tight spaces in a CO2 compressor, the spaces between the pistons where lubricant can be distributed, for example, in the drive chamber, become narrower and narrower. The larger the peripheral housing region covered by the piston brace is compared to the exposed peripheral region of the housing, the more difficult is it to supply lubricant to this region. If in tilting plate machines or tilting ring machines of this type, such as for CO2 applications, the degree of coverage by the piston brace becomes relatively high so that there are only small gaps between the individual piston brace regions for introducing lubricant between the peripheral regions, insufficient lubricant supply and friction damage may occur in this area.